Malaria

Causes and Risks:
Malaria is caused by a parasite that is transmitted from one human to another by the bite of infected Anopheles mosquitoes. In humans, the parasites (called sporozoites) migrate to the liver where they mature and release another form, the merozoites. These enter the bloodstream and infect the red blood cells. The parasites multiply inside the red blood cells, which then rupture within 48 to 72 hours, infecting more red blood cells. The symptoms occur in cycles of 48 to 72 hours. The majority of symptoms are caused by the massive release of merozoites into the bloodstream, the anemia caused by the destruction of the red blood cells, and the problems caused by large amounts of free hemoglobin released into the circulation after red blood cells rupture.

Malaria can also be transmitted congenitally (from a mother to her unborn baby) and by blood transfusions. Malaria can be carried by mosquitoes in temperate climates, but the parasite disappears over the winter.

The disease is a major health problem in much of the tropics and subtropics. More than 200 million people in the world have malaria. It presents the greatest disease hazard for travelers to warm climates. In some areas of the world, mosquitoes that carry malaria have developed resistance to insecticides , while the parasites have developed resistance to antibiotics. This has led to difficulty in controlling both the rate of infection and spread of this disease. Falciparum malaria, one of four different types, affects a greater proportion of the red blood cells than the other types and is much more serious. It can be fatal within a few hours of the first symptoms.

Prevention:
Most people living in malaria-prevalent areas have acquired some immunity to the disease. Visitors will not have immunity and need to take preventive medications. Preventive medications should be taken even by pregnant women, because the risk to the fetus from the medication is less than the risk of acquiring a congenital infection. People on antimalarial medications may still become infected. Avoid mosquito bites by wearing protective clothing over the arms and legs, using screens on windows, and using insect repellent.

Chloroquine has been the drug of choice for protection from malaria. With emerging resistance, it is now only indicated for use in areas where Plasmodium vivax, P. oval, and P. malariae are present. Falciparum malaria is becoming increasingly resistant to antimalarial medications.

For travelers headed for areas of endemic Falciparum malaria, the present drug of choice is mefloquine. Mefloquine has been approved by the FDA and is effective at preventing Falciparum malaria. Other drugs include Proguanil (available only in Africa) and Fansidar (pyrimeth/sulfadoxine).

Travelers can call the CDC for information on types of malaria in a given geographical area, preventive drugs, and times of the season to avoid travel.

For information, call:
(404) 332-4555
(404) 639-3311

Symptoms:



Signs and Tests:
Physical examination may show an enlarged liver ( hepatomegaly ) and an enlarged spleen ( splenomegaly ).

Tests:
Malaria blood smears given at 6- to 12-hour intervals confirm the diagnosis.


Treatment:
FOR TRAVELERS
Antimalarial drugs can be prescribed for visitors to areas where malaria is prevalent. Treatment should begin two weeks before entering the area, and continue for 4 weeks after leaving the area. The types of antimalarial medications prescribed will depend on the drug-resistance patterns in the areas to be visited. Chloroquine, quinine, and the combination of pyrimethamine and sulfadoxine are some examples of drugs you may receive. It is very important to know the countries and areas you will be visiting to obtain appropriate preventive support for malaria.

FOR ACTIVE INFECTIONS
Malaria, especially Falciparum malaria, is a medical emergency requiring hospitalization. Chloroquine is the most frequently used antimalarial medication, but quinidine or quinine, or the combination of pyrimethamine and sulfadoxine are given for chloroquine-resistant infections.

Prognosis:
The outcome is expected to be good in most cases of malaria with treatment, but poor in Falciparum infection with complications.

Complications:



Call Your Healthcare Provider:
Call your health care provider if you develop fever and headache after visiting the tropics.


Malaria is a disease caused by parasites that are carried by mosquitoes. Once in the bloodstream, the parasite inhabits the red blood cell (RBC). This picture shows purple-stained malaria parasites inside red blood cells.



There are many different species of mosquito, some of which carry some of the worlds most common and most economically important infectious diseases. Malaria and yellow fever are two of the most important diseases they carry. Others include encephalitis (viral), dengue fever, and leishmaniasis. (Courtesy of the Centers for Disease Control.)



This illustration shows an adult southern house mosquito. This mosquito feeds on blood and is the carrier of many diseases, such as malaria, dengue fever, yellow fever, and others. (Courtesy of the Centers for Disease Control.)



Mosquitoes lay their eggs in still or stagnant water. The eggs hatch into a carnivorous larval stage before developing into flying mosquitoes. (Courtesy of the Centers for Disease Control.)



This picture shows mosquito larvae, most of which will become blood-sucking, disease-carrying mosquitoes. (Courtesy of the Centers for Disease Control.)



These are mosquito pupa. This is another stage in the development of the mosquito. (Courtesy of the Centers for Disease Control.)



Malarial parasites are visible within the red blood cells. They are stained a dark bluish color.



Malaria is a disease caused by parasites. This picture shows dark orange-stained malaria parasites inside red blood cells (a) and outside the cells (b). Note the large cells that look like targets; it is unknown how these target cells are related to this disease.



Jaundice results when bilirubin, a yellowish pigment, builds up to high levels in the blood stream. Bilirubin is a breakdown product of hemoglobin, the red oxygen-carrying pigment found in red blood cells (RBCs). The liver and biliary system are responsible for ridding the body of bilirubin. Jaundice usually indicates liver disease or obstruction of the biliary system.